Fluid pressure braking system



atented Mar. 28; 1939 FLUID PRESSURE BRAKING SYSTEM Herbert 0. Bowen, Detroit, Mich., assignoroto Hydraulic Brake Company, Detroit, Micln, a corporation of California Application September 17, 1936, Serial No. 101,201

10 Claims. (01. 6054.5)

This invention relates to braking systems for motor vehicles, and more particularly to fluid pressure braking systems for motor vehicles.

The invention comprehends a relatively simple At the base of the reservoir are two corresponding cylinders I8 and 20, arranged in parallel relation to one another and interconnected as by a passage 22. The cylinder [8 has a large fluid pressure braking system for motor vehicles chamber 24 and a concentrically arranged small 5 including two separate braking systems arranged chamber 26 providing at the junction of the two for concomitant operation and interconnected so chambers an annular shoulder 28. The large as to provide for equalization of pressures in the chamber has ports 30 and 32 providing commurespective systems.- nications between the large chamber and. the

An object of the invention is to provide a du-' reservoir, and the small chamber has a head 34 10 plex braking system for motor vehicles having a provided with a discharge port 36 controlled as single operating means common to both systems. by a. two-way valve 38. Similarly, the cylinder Another object of the invention is to provide 20 has a large chamber 40 and a concentrically a duplex braking system for motorvehicles havarranged small chamber 42 providing at the junclng means for equalizing pressures produced in tion of the two chambers an annular shoulder 15 the respective systems. I 44. The large chamber has ports 46 and 48 pro- Another object of the invention is to provide a viding communications between the large chamduplexbraking system for motor vehicles includber 40 and the reservoir. The small chamber 42 ing one system for actuating brakes'associated has a head 50 provided with a discharge port with the front wheels of the vehicle and the 52 controlled by a two-way valve 54. 20

1 other system for actuating brakes associated with The discharge port 36 in the head 34 of the the rear .wheels of the vehicle, and to so intercylinder' I 8 is connected by a fluid pressure deconnect the systems as to provide for equalizalivery pipe or conduit 56 and branch conduits tion of pressures in the respective systems and 58 and 60 to fluid pressure actuated motors 62 also to provide for operation of one of the sysarrangedfor actuation of a pair of brakes as- 25 tems in the event of failure of the other system. sociated with the W eels o a motor ve e, d

w A further object of the invention is to provide the. discharge port 52 of the small chamber 40 a duplex braking system for motor vehicles in of the cylinder 20 is connected by a fluid preswhich failure or one system, due to breakage or su d v ry p or conduit 64 a d an h leakage, during a braking operation, does not duits 66 and 68 to fluid pressure actuated mo- 30 materially affect the other system. tors 10 arranged for actuation of another pair Other objects of the invention will appear 0f brakes for the vehicle. from the following description taken in connec- The brakes are preferably of Conventional p tion with the drawings forming a part of this each including fixed suppor or bac plate specification, and in which, 12, a rotatable drum 14 associated therewith, a 35 Fig. 1 is a diagrammatical illustration of a fluid pair f r sp n t n ts or s s pressure braking system embodying the inven- 75 p ot 0n the backing plate, a fluid Pressure tion; motor corresponding to the motors 62 and 10 Fig. 2 is a longitudinal, sectional view of a moun ed on t e' k plate w n e s fluid pressure producing device coupled in the arable ends f h ho an a r ile pring 40 system; 18 connected between the shoes.

Fig. 3 is a vertical, sectional view of the fluid Pistons 80 and 82, reciprocable in the respecpressure producing device; Y tive cylinders l8 and 20, are retained against Fig. 4 is a cross-sectional view of the fluid presdisplacement by washers 84 supported on retainsure producing devices taken substantially on me rin s 86 se te in circumferential r v i 45 line 4-4, Fig. 2; and the wall of the cylinders adjacent the open ends Fig. 5 is a fragmentary view similar to Fig. 3, thereof. Each of the pistons includes a head but showing the shell engaging the piston to cut 88, a skirt 90 carrying a leak-proof washer 92 off communication between the large and small for inhibiting the s p of fl d fr m t e ylchambers of the cylinder. inder past the piston, and a reduced body por- 50 Referring to the drawings for more specific tion 94 providin in Conjunction with e W l details of the invention, l0 represents a reservoir of the cylinder an annular chamber 96 commuhaving a filling opening l2, which may be closed nicatlng with the reservoir. The piston has as by a plug l4 provided with openings 5 for spaced openings 98 in its head providing comventing the reservoir to the atmosphere.

munication's between the annular chamber 96 and that portion of the cylinder forward of the head, and formed on the head is a concentric extension I projecting into the small chamber of the cylinder. The openings 98 in the head of the piston are controlled by a collapsible leakproof cup I 02 seated on the head of the piston. A washer I04, the purpose of which will hereinafter appear, is seated on the annular shoulder at the junction of the large and small chambers of the cylinder, and 'a, spring I06 sleeved on the extension I00 between the washer I04 and the cup I02 serves to retain the washer and the cup. against displacement and also to return the piston to its retracted position.

The free end of the extension I00 has a projection I08 undercut as at I I0, and on the circumference of the extension are a plurality of grooves II2 for the passage of fluid. A shell II4 sleeved on the end of the extension I00 and normally seated on the washer I04 has a concentric opening II6 for the reception of the projection I08, and the perimeter of the shell defining the opening is undercut as at II8 for cooperation with the undercut IIO on the'projection I08 so as to provide for free passage of fluid upon relative movement of the extension I 00 and the shell H4. A leak-proof cup I20 seated on the shell II4 has a concentric opening I22. The perimeter of the cup defining the opening I 20 overhangs the opening H6 in the shell and isengaged by the face of the projection I08 on the extension when the projection enters the opening in the shell so as to inhibitpassage of fluid through the opening in the shell. A spring I2I interposed between the cup I20 and the two-way. valve controlling the exhaust port serves to retain the cup and the valve against displacement.

The pistons 80 and 82 have in their backs recesses I24 and I26 for the reception of thrust pins I28 and I30 threaded in a suitable coupling I32 connected as by a flexible boot I34 to the open ends of the cylinders I8 and 20v for the exclusion of dust and other foreign substances from the cylinders. A rod I36 connects the coupling I32 to a foot pedal lever I38 pivoted,

on a suitable support I40 an d connected bya retractile spring I42 to a fixed support,

In a normal braking operation, upon depressing the foot pedal lever I38, force is transmitted therefrom through the coupling I32 and thrust pins I28 and I30 to the pistons 80 and 82, resulting in moving the pistons on the compression stroke. During the initial movement of the pistons on the compression stroke, the cups I02 on the heads of the pistons close the ports 32 and 48, and thereafter the fluid in the cylinders I8 and 20 forward of the heads of the pistons is displaced through the openings H6 in the shells II4, the openings I22 in the cups I20, and the small chambers of the cyinders, past the two-way valves 38 and 54, and through the discharge ports 36 and 52 and fluid pressure delivery pipes 58 and 54 and the branches thereof into the fluid pressure actuated motors 62 and I0, causing actuation of the motors with the resultant movement of the shoes 16 intgengagement with the drums I4 against the resistance of the retractile springs 18. During this movement of the pistons relatively rapid displacement takes place of the fluid in the cylinders I8 and 20, with the result that the friction elements I are quickly moved into engagement with the drums 14.

The cylinders are interconnected by the passage 22, and because of this there is perfect equalization of the pressures in the respective systems. As the pistons advance on the compression stroke, movement of the fluid through the cylinder lifts the shells II4 from their seats on the washers I04 sufllciently to provide for an uninterrupted flow of the fluid through the openings in the shells I I4 and the openings in the cup I20. This condition prevails until the pressures in the large and small chambers of the respective cylinders balance, whereupon the'springs,

I2I interposed between the cups I and the twoway valves urge the shells II4 to their seats on the extensions I00, in which position the projections I08 are received by the openings in the shells H4 and seal against the cups I20 to inhibit the flow of fluid through the shells and cups. In the normal operation of the mechanism, the pressures in the large and small chambers of the cylinders balance only when the forward motion of the pistons ceases.

Under these conditions, should either of the systems fail, due to leakage or breakage, the-other system is in -no way effected. This is because of a differential of pressure in the large and small chamber of the particular cylinder connected with the system remaining operative. After the loss of fluid in the ruptured system, on subsequent operations the cylinder coupled with the ruptured system is inefiective for producing pressure, and since the cylinders I8 and 20 are interconnected by the passage 22, no material pressure can be had in the cylinder connected to the system remaining effective except in the small chamber of the cylinder forward of the shell II4. This pressure is sufliclent to effectively operate one set of the brakes. Under this condition it will be perfectly clear to the operator of the'vehicle that a loss of braking power has been sustained.

However, notwithstanding this loss, sufficient braking power will be sustained for safe operation of the vehicle until such time as repairs the braking system may be made. j

After a normal braking application, upon release of the foot pedal lever I38, the lever is returned to its normal position under the influence of the retractile spring I42. As the foot pedal lever returns to its normal position, the thrust pins I28 and I are retracted, resulting in releasing the pistons 80 and 82, whereupon the springs I06 become. effective to return the pistons to their retracted positions. As the pistons 80 and 82 return to their retracted positions, partial vacuums are created in the cylinders forward of the heads of the pistons, resulting in drawing fluid from the reservoir into the annular chambers 96, thence through the passages in the heads of the pistons, past the cups I02, into that portion of the respective cylinders forward of the pistons, completely filling the-cylinders. During this operation fluid is also returning to the cylinders I8 and 20 from the fluid-pressure actuated motors 62 and under the influence of the retractile springs I8 connecting the respective pairs of friction elements I6 of the brakes. Accordingly, the cylinders receive more fluid than is essential to completely fill the cylinders, and this surplus of fluid is returned to the reservoir I0 by way of the compensating ports 32 and48.

Although this invention has been described in connection with certain specific embodiments, the principles involved are susceptible of numerous other applications that will readily occur to. persons skilled in the art. The invention is, therefore, to be limited only by thescope of the appended claims. I

Having thus described the various features of the invention, what I- claim as new and desire to secure by Letters Patent is:--

1. A fluid braking system comprising a pair of interconnected fluid pressure producing devices each incliiding a large chamber and a small chamber, said large chambers being interconnected and each of said small chambers being provided with an outlet, and means operative upon attaining a balanced pressure in the chambers to segregate alarge chamber from a small one.

2. A fluid braking system comprising a pair of cooperative interconnected fluid pressure producing devices each including a cylinder having a large chamber and a small chamber, said large chambers being interconnected and each of said small chambers being provided with an outlet, a piston in the cylinder for producing pressure in the chambers, and means cooperating with the pistons upon attaining a balanced pressure in the chambers to segregate the large chambers from the small chambers.

3. A fluid braking system comprising a pair of corresponding cylinders each having a large chamber and a concentrically arranged small chamber communicating with the large chamber,

a passage connecting the large chamber of one of the cylinders with the large chamber of the other cylinder, each or said small chambers having an outlet, pistons movable in the cylinders for producing pressure in the chambers, and means cooperating with the pistons upon attaining'a balance of pressure in the chambers to segregate the large chambers from the small chambers.

4. A fluid braking system comprising a pair of corresponding cylinders each having a large chamber and a concentrically arranged small chamber communicating with the large chamber, a passage connecting the large chamber of one of the cylinders to the large chamber of the other cylinder, each or said small chambers being provided with an outlet, pistons movable in the cylinders for creating pressures in the chambers, and means cooperating with the pistons upon attaining uniform pressures in the respective large and small chambers to segregate the large chambers from the small chambers.

5. A fluid braking system including a pair of corresponding interconnected fluid pressure producing devices each having a large chamber and a small chamber arranged concentrically to and communicating with the large chamber, said large chambers being interconnected and each of said small chambers being provided with an outlet, a fluid pressure actuated motor connected to each of the small chambers, means for actuating the devices, and means operative to segregate the respective large and small chambers upon attaining uniform pressures in the large and small chambers.

6. A braking system comprising a pair of interconnected fluid pressure producing devices each including a large chamber and a small chamber communicating with the large chamber, said large chambers being interconnected and each of said small chambers being provided with an outlet, fluid pressure actuated motors connected to each of the outlets, means for actuating the devices in unison, and means in each device to segreate the large chamber from the small cham r of the same device upon attaining uni- Iorm pressures in bpth chambers of the same device.

'7. In a fluid braking system, a pressure producing device comprising a cylinder having a large chamber and a small chamber'providing an annular shoulder at the junction of the chambers, a piston movable in the large chamber having an extension projecting into the small chamber, a washer seated on the annular shoulder, a spring interposed between the washer and the piston, a movable shell in the small'chamber normally seated on the washer and adapted to cooperate with the extension on the piston to segregate one chamber from the other, and a spring interposed between the shell and'the head of the cylinder.

8. In a fluid bralring system, a pressure producing device comprising a cylinder having a large chamber and a small chamber providing at the junction of the chambers an annular shoulder, a head on the small chamber provided with a discharge port, a valve controlling the discharge port, a reciprocable piston in the large chamber having an extension projecting into the small chamber, a collapsible leak-proof cup on the head of the piston, a washer on the annular shoulder, a spring interposed between the cup and the washer,-a reciprocable shell in the small chamber normally seated on 'the washer and adapted to cooperate with the extension on the piston to segregate one chamber from the other, a leak-proof cup on the shell, and a spring interposed between the cup and the valve controlling the discharge port.

9. In a fluid braking system, a. ,pair of interconnected corresponding fluid pressure producing devices each including a cylinder having a large chamber and a small chamber providing an annular shoulder at the junction of the chambers, a head on the small chamber having a discharge port, a valve controlling the port, a reciprocable piston in the large chamber having an extension projecting into the small chamber, a collapsible leak-proof cup on the head of the piston, a washer on the annular shoulder, a spring interposed between the cup and washer, a reciprocable shell in the small chamber normally seated on the washer and adapted for cooperation with the extension on the piston to segregate one chamber from the other, a leak-proof cup on the shell,

provided with a discharge port, a valve con'-,

trolling the-discharge port, a reciprocable piston in the large chamber having an extension projecting into the small chamber, a collapsible leakproof cup on the head of the piston, a washer on the annular shoulder, a spring interposed between the cup and the washer, a reciprocable shell in the small chamber normally seated on the washer and adapted to cooperate with the extension on the piston to segregate one chamber from the other, a leak-proof cup on the shell, and a spring interposed between the cup and the valve controlling the discharge port, fluid pressure actuated motors connected to each device, and means for actuating the devices.

HERBERT c. BOWEN. 

